Presentation at 2015 Bioenergy Technologies Office Peer Review March 23, 2015
Presentation at Auto/Ag/Ethanol Meeting USCAR August 18, 2015
Share and discuss provisional findings from coordinated DOE national laboratory studies on the opportunities and challenges associated with the deployment of high octane, mid-level ethanol blend transportation fuels.
Presentation to Hudson Institute Fueling American Growth Washington, DC May 7, 2015
Presentation at National Ethanol Conference Grapevine, TX February 20, 2015
Presentation at Biomass 2013 Meeting
The compatibility of elastomeric materials used in fuel storage and dispensing applications was determined for test fuels
representing neat gasoline and gasoline blends containing 10 and 17 vol.% ethanol, and 16 and 24 vol.% isobutanol. The
actual test fuel chemistries were based on the aggressive formulations described in SAE J1681 for oxygenated gasoline.
Elastomer specimens of fluorocarbon, fluorosilicone, acrylonitrile rubber (NBR), polyurethane, neoprene, styrene
butadiene rubber (SBR) and silicone were exposed to the test fuels for 4 weeks at 60°C. After measuring the wetted
volume and hardness, the specimens were dried for 20 hours at 60°C and then remeasured for volume and hardness.
Dynamic mechanical analysis (DMA) was also performed to determine the glass transition temperature (Tg).
Comparison to the original values showed that all elastomer materials experienced volume expansion and softening when
wetted by the test fuels. The fluorocarbons underwent the least amount of swelling (100%). The level of swelling for each elastomer was higher for the test
fuels containing the alcohol additions. In general, ethanol produced slightly higher swell than the oxygen equivalent level of
isobutanol. When dried, the fluorocarbon specimens were slightly swollen (relative to the baseline values) due to fuel
retention. The NBRs and neoprene exhibited shrinkage and embrittlement associated with the extraction of plasticizers.
SBR also experienced shrinkage (after drying) but its hardness returned to the baseline value. The dried volumes (and
hardness values) of the silicone, SBR and fluorosilicone rubbers closely matched their original values, but the
polyurethane specimen showed degradation with exposure to the test fuels containing ethanol or isobutanol. The DMA
results showed that the test fuels effectively decreased Tg for the fluorocarbons, but increased Tg for the NBR materials.
The Tg values other elastomers were not affected by the test fuels.
The compatibility of plastic materials used in fuel storage and dispensing applications was determined for an off-highway diesel fuel
and a blend containing 20% bio-oil (Bio20) derived from a fast pyrolysis process. Bio20 is not to be confused with B20, which is a
diesel blend containing 20% biodiesel. The feedstock, processing, and chemistry of biodiesel are markedly different from bio-oil.
Plastic materials included those identified for use as seals, coatings, piping and fiberglass resins, but many are also used in vehicle
fueling systems. The plastic specimens were exposed to the two fuel types for 16 weeks at 60°C. After measuring the wetted volume
and hardness, the specimens were dried for 65 hours at 60°C and then remeasured to determine extent of property change. A solubility
analysis was performed to better understand the performance of plastic materials in fuel blends composed of bio-oil and diesel.
All of the plastic materials evaluated in this study exhibited higher solubility (volume swell) with the Bio20 fuel blend. This result was
predicted by the solubility analysis. However, there were two notable exceptions; the volume swell results for high density
polyethylene (HDPE) and polypropylene (PP) did not correlate with their respective solubility curves. HDPE and PP were also unique
in that they were the only two plastics that exhibited pronounced volume expansion in the baseline diesel test fuel.
The plastic materials which showed the best compatibility to the bio-oil blend were the barrier plastics polypropylene sulfide (PPS),
polyethylene terephthalate (PET or Mylar™), and polytetrafluoroethylene (PTFE or Teflon™). Polyvinylidene fluoride (PVDF or
Kynar™) is also used extensively as a permeation barrier material; however, it swelled over 15% when exposed to Bio20. Four grades
of nylon were evaluated and the petroleum-derived nylons (Nylon 6, Nylon 6,6, and Nylon 12) showed good compatibility with the
test fuels. In contrast, Nylon 11, which is derived from vegetable oil, expanded over 4% with Bio20. HDPE also swelled around 4%,
but did so with both test fuels. Two acetal materials and polybutylene terephthalate (PBT) were also observed to swell to 4% with
Bio20. Four fiberglass resins were included in the study and they exhibited 10-18% volume expansion. High volume swell was also
noted for PP, the PET polyethylene - glycol copolymer (PETG), and polythiourea (PTU). PP also expanded over 15% following
exposure to the baseline diesel test fuel.
The compatibility of plastic materials used in fuel storage and dispensing applications was determined for a test fuel representing
gasoline blended with 10% ethanol. Prior investigations were performed on gasoline fuels containing 25, 50 and 85% ethanol, but the
knowledge gap existing from 0 to 25% ethanol precluded accurate compatibility assessment of low level blends, especially for the
current E10 fuel (gasoline containing 10% ethanol) used in most filling stations, and the recently accepted E15 fuel blend (gasoline
blended with up to15% ethanol).
For the majority of the plastic materials evaluated in this study, the wet volume swell (which is the parameter most commonly used to
assess compatibility) was higher for fuels containing 25% ethanol, while the volume swell accompanying E10 was much lower.
However, several materials, such as polyvinylidene fluoride (PVDF), fiberglass resins, and the polyethylene terephthalate co-polymer
(PETG) exhibited similar volume expansions with both 10 and 25% ethanol.
In the second part of this study, the compatibility performance of the infrastructure plastics in the E10 test fuel was compared to a test
fuel containing 16% isobutanol (which has the same oxygen level as E10). The measured property changes (volume and hardness) in
these two fuels were similar for the majority of the plastics tested. However, Nylon 6, Nylon 6,6, and the vinyl ester fiberglass resin
showed much better compatibility with a 16% isobutanol blend than with a blend containing 10% ethanol.
The compatibility of plastic materials used in fuel storage and dispensing applications was determined for test fuels representing gasoline blended with 25 vol.% ethanol and gasoline blended with 16 and 24 vol.% isobutanol. Plastic materials included those used in flexible plastic piping and fiberglass resins. Other commonly used plastic materials were also evaluated. The plastic specimens were exposed to Fuel C, CE25a, CiBu16a, and CiBu24a for 16 weeks at 60oC. After measuring the wetted volume and hardness, the specimens were dried for 65 hours at 60oC and then remeasured for volume and hardness. Dynamic mechanical analysis (DMA) was also measured on the dried specimens.
The plastic materials used as permeation barriers exhibited the least amount of properly change when exposed to the test fuels. The performance of nylon was highly dependent on the grade; of the four nylons evaluated, Nylon 6 and Nylon 6,6 showed the lowest property change following exposure to Fuel C, CiBu16a and CiBu24s, but swelled over 7% when exposed to CE25a. Acetal and polybutylene terephthalate (PBT) swelled around 5% with exposure to the test fuels, while high density polyethylene (HDPE) swelled around 10% for each test fuel. The remaining thermoplastics swelled to higher values and in the case of polypropylene, dissolution occurred with exposure to CE25a. The fiberglass resins experience more swelling in CE25a that with the Fuel C or the two isobutanol blends. In general, the plastics exhibited a positive volume change when dried, which was attributed to fuel retention. In addition CE25a produced a higher degree of property change than the other test fuels.